Haploidie

Haploidie refers to a state in which a cell or organism possesses a single set of chromosomes. In contrast, diploid organisms have two sets of chromosomes, one inherited from each parent. Haploid cells, often denoted as 'n', contain half the number of chromosomes found in somatic (body) cells of a diploid organism.

The most common examples of haploid cells are gametes, which are reproductive cells such as sperm and egg cells in animals and humans. These gametes are produced through a process called meiosis, which reduces the chromosome number by half. When a haploid sperm fertilizes a haploid egg, the resulting zygote becomes diploid, restoring the full complement of chromosomes.

Some organisms, such as bacteria, archaea, and fungi, exist primarily in a haploid state throughout their life cycle. In these organisms, cell division occurs through mitosis, where a haploid cell duplicates its genetic material and divides into two identical haploid daughter cells.

Certain stages in the life cycle of plants and algae also involve haploid phases. For example, in plants, the gametophyte generation is haploid and produces gametes. The alternation of generations, a common phenomenon in these organisms, involves a cycle between haploid and diploid phases. Understanding haploidie is fundamental to comprehending genetics, reproduction, and the diversity of life forms.